Add process plugin to skip duplicate records

@danflanagan8 very belated Thank you! -- and, I've ended up in a situation where the thing I was doing is off my plate for the foreseeable future, which is, very bummer.

But, I'm going to keep this tab open so I can try your tips when I have a slow week (I've actually had some slow weeks recently -- too bad I didn't think of this then) -- I definitely want to try Migrate Conditions.

Thanks again!!